In 1933 Japan occupied the Chinese province of Jehol and initiated a large-scale warfare in 1937 that alarmed the international community. Following the clash with the Soviets in Nomonhan, Japan lost access to oil concessions from Northern Sakhalin.
When France capitulated in June 1940, Japan moved into Northern French Indochina and the U.S. Administration reacted by banning the export of essential defense materials: aviation motors, high-octane aviation fuel, lubricants, iron and steel scrap. The embargo was expanded in July 1941 to all grades of oil and the British and the Dutch followed suit, embargoing exports of copper, tin, bauxite, rubber and petroleum to Japan from their colonies in Southern Asia. The Allies were putting Japan in an untenable position that would force oil-starved Japan to seize the oil fields of the Dutch East Indies.
The 91octane for aircraft was unavailable, they had to work with 87 octane, or even sometimes mixed with a volatile oil extracted from pine tree roots that lowered the fuel to 85 octane. It was so contaminated with impurities that American Jeeps that used this fuel during occupation suffered engine failures.
In 1945 the Ki.115 could use several types of second hand conventional engines but it required 80 octane gasoline which was almost non-existent in Japan due to the naval blockade. On the other hand, the Ne-20 could work with a mixture of wood turpentine and charcoal, although the battered Japanese industry could not manufacture them in high numbers.
The Japanese scientists found the solution to this situation with the mass production of pulsejet engines based on the Argus As 109-014 scale drawings that the I-8 submarine had brought from Germany in 1943. It used Benzol as fuel during the flying tests, although it could also work with low quality oil or heavy kerosene. It was expected that the operational version would burn 1,600 lt of crude pine root oil that the local chemical industry produced as ersatz fuel.
